Unit 3: Cardiovascular Physiology Flashcards
What four components of the cardiovascular system apply to homeostasis of cells?
Provides nutrient transport via the GI system, important gas exchange such as oxygen and carbon dioxide via the respiratory system, hormone transport, and works with the skin and muscles to regulate temperature.
Compare the cardiovascular system to a water distribution system.
The heart is the pump, the blood vessels are the plumbing, and the blood is the fluid.
What is the average blood volume of a human?
5.5 Liters
What are the three components of blood, their proportion (%) and of what do they comprise?
The plasma (55-58%) is the lightest, contains plasma proteins, and is part of the extracellular fluid. The Buffy coat is 1% or less, and consists of leukocytes and platelets. The red blood cells, also called erthyrocytes, are bout 42-45% of the blood, and are responsible for oxygen transport.
The heart is a ___ pump
Dual
Arteries
From the heart to the capillary beds
Veins
From the capillary beds to the heart
Are all arteries oxygen rich?
No, the pulmonary trunk and arteries are indeed moving away from the heart, but are going toward the lungs to become oxygenated.
In terms of blood flow, every organ system is in ___ with the lungs, and in ____ to each other.
series with the lungs, and in parallel with each other
Move from the right atrium —>blood circuit
Right atrium, right ventricle, pulmonary trunk and arteries, arterioles, pulmonary capillaries, pulmonary venules, pulmonary veins, left atrium, left ventricle, Systemic arteries, systemic arterioles, systemic capillaries, systemic venules, systemic veins, vena cava, right atrium again.
Explain how a single capillary is high resistance, but the capillary bed is low resistance
One capillary has a very small diameter providing incredible resistance, however many capillaries together are essentially no barrier.
What is one reason it is good that systemic organs are in parallel?
If one flow to an organ is blocked, the others are not.
General Hemodynamic Equation
Flow = C x P
C in terms of R
C = 1/R
Resistance equation
R = (8Lnu) / (pi*(r^4))
What is the greatest factor to determining resistance?
The radius of the tube
Given two different radii tubes, what will happen to flow rate, given the same change in pressure for the two tubes?
The tube with the larger radius will exhibit a much larger increase in flow rate per unit step in pressure.
Epicardium
Outermost layer of the actual heart
Pericardium
Outermost sac that surround the heart encasing it in pericardial fluid for minimized friction.
Myocardium
Middle muscle layer of the heart
Which side of the heart has a tricuspid valve, and which the bicuspid valve?
The left side of the heart has a bicuspid, and the right side has the tricuspid valve. Both valves separate the atria and ventricles.
Papillary muscles
Prevent force to avoid the AV valves from inverting
Chord tendineae
Connect the AV valves to the papillary muscles
Semilunar valves
the pulmonic and aortic valves
Heart Muscle Cells [appearance, membrane excitability, nuclei, mitochondria consistency, and electrical continuity]
Striated due to sarcomeres, have excitable membranes via T tubules, small, with a single nucleus, 40% mitochondria, intercalated disks, desmosomes, and gap junctions for electrical continuity.
Excitation Sequence
SA node excitation, then slow atrial contraction (P Wave) toward the AV node, which delays for 0.1 seconds. Atrial relaxation (Q wave), then traveling down bundle of His (start of R wave) then traveling rapidly through Purkinje fibers to create ventricle contraction (large part of R wave), then S and T waves.
Design/Function: Why are there no valves to gate the entry of venous blood into the atrium?
The blood returning from the capillary bed has very little pressure
Design/Function: Why is there no fast conduction in the atria?
The slow conduction slowly moves the blood like toothpaste
Design/Function: Why is there fast conduction in the ventricles?
Simultaneous activation of muscle creates maximal force.
Design/Function: Why are the ventricles gated by one way valves?
The force of the ventricles would cause blood to rush back toward the atria.
Resting relative concentrations of K, Ca, Na, Cl
Na,Cl, Ca high outside, K high inside.
Typical Nernst potential for Sodium
+65
Typical Nernst potential for Potassium
-90
Depolarization in a cardiac muscle cell
Starts with action potential that opens Na+ channels, and quickly inactivates. L type Ca2+ channels then open, acting the same way as Na+, however, staying open for “long” time before they too inactivate. At this point, there is brief activation of Potassium channels that re-polarizes the cell to -90.
How long is the refractory period of a cardiac cell, and why?
Inactivation of Na+ channels cause a refractory period longer than the length of an action potential.
F type channels
Pacemaker: slow to open at HYPERPOLARIZATION (-60mV),close at depolarization. permeable to both Na+ and K+, however, at hyper polarization more to Na+.
F,T,L,K channel working together in Nodal Cells
during HYPERPOLARIZATION, the F type channels open and start to depolarize the cell, but close quickly to be picked up by T type calcium channels which bring the potential up towards 0, at which point L type calcium channels above 0, which K+ channels will polarize again toward F type threshold.
T type channels
Open on depolarization, -50mV, and relatively quick inactivation compared to L type. Recover from inactivation upon hyper polarization.
Cardiac Ion Channels: In general, Nodal cells have:
F,T,L,K
Cardiac Ion Channels: In general, myocytes have :
Na,L,K
Cardiac Ion Channels: In general, Fast conducting channels have:
all types, FTLKNa
Conduction Velocity
rate of increase in voltage in the upstroke of the action potential. Determined by events after threshold: Sodium channels in muscle and purkinje fibers, and L type calcium channels in nodal cells
Conduction Frequency
number of action potentials per unit time, Determined by the events before threshold: F-type sodium channels in nodal cells, and the T type Ca2+
P wave
depolarization of the SA node to AV node. Atria contract
QRS complex
ventricular depolarization that immediately precedes ventricular contraction
T wave
caused by ventricular repolarization
Why is atrial re polarization not clearly seen in the ECG
Atrial depolarization is obscured by the QRS complex because ventricular depolarization is much greater.
Arrhythmia
uncoordinated atrial and ventricular contraction caused by conduction system issue
Fibrillation
rapid and irregular contraction where SA node is no longer controlling heart rate
Is an atrial or ventricular fibrillation more dangerous?
Ventricular
Pacemakers
Issue a timed stimulus to the heart
Excitation Contraction Coupling in Cardiac Cells
Depolarization leads to opening of L type calcium channels in T tubules, which influx Ca 2+ deep into the cell. Calcium binds to ryanodine on the SR which releases additional stored Ca 2+ from inside the cell. The combined Ca2+ activates troponin etc. like in skeletal muscle.
What is true about the refractory period in cardiac muscle cells?
The refractory period is nearly as long as the action potential, which means that there is no tetany.
Systole
Contraction
Diastole
Relaxation
Mechanical Events of Heart
Please refer to a whiteboard. Too complex.
Dicrotic Notch
moment when right after ventricles have contracted and released blood into the aorta, the semilunar aortic valve closes. The aorta now has a moment of higher pressure than the ventricle. The blood pushes back against the SL aortic valve and a sound is heart, dicrotic notch.
First heart sound
AV valves close at ventricular ejection
second heart sound
Dicrotic Notch, closure of SL valves
Lub
AV closure
Dup
Semilunar
Whistle
Stenotic Valve, roughly opened
Gurgle
Insufficient valve, not completely closed
Resting heart output volume
5 L
Active heart output volume
25 L
Cardiac Output =
CO = HR x SV
Parasympathetic [nerve, NT, receptor]
Vagus nerve, acetylcholine, muscarinic
Sympathetic [nerve, NT, receptor]
Thoracic spinal nerve, norepinephrine, either from nervous or hormone, beta adrenergic receptor
Sympathetic Nerves Innervate:
atria and ventricles
Parasympathetic Nerves Innervate:
atria
Sympathetic: SA node frequency is affected by what permeability?
F-type Na channels
Sympathetic: Stroke Volume increased from what permeability?
L-type Ca2+ channels
Parasympathetic: SA node frequency lowered with what permeabilities?
Increased K+ leak channels, decreased F-type Na permeability.
What happens to the action potential curve for sympathetic response?
slope below the threshold increases due to increased F-type Na permeability. No other changes in waveform.
Stroke Volume
difference between end diastolic and end systolic volumes
Frank Starling Relationship–>Stroke Volume
The degree of stroke volume is partially due to the preload from amount of blood pre-stretching the cardiac cells. Muscles able to produce more tension the more initially stretched out they are.
How do the sympathetic nerves increase the stroke volume?
They lower ESV by increased contraction by increasing Ca 2+ levels.
How does the sympathetic system increase Ca 2+ levels?
Addition of norepinephrine and epinephrine to beta adrenergic receptor which activates cAMP dependent kinase through adenylyl cyclase protein. Active cAMP-dependent kinase stimulates L type Ca2+ channels, thin filaments, cross bridge cycling, and ryanodine receptors that all provide more contraction.
Ejection Fraction
EF = SV/EDV
What does increased contractility do to the Ejection Fraction?
It increases. Your stroke volume approaches the full end diastolic volume available to exude.
Veins and Arteries: Which contain more smooth muscle and connective tissue?
Arteries
Veins and Arteries: Pressure Reservoirs
Arteries
Veins and Arteries: Volume Reservoirs
Veins
Compliance Equation
Change in volume / change in pressure
Elasticity Equation
Change in pressure / change in volume
MAP
Mean Arterial Pressure: Diastolic Pressure + (1/3)*(Systolic-Diastolic Pressure)
Veins and Arteries: Which are more compliant?
Veins
Veins and Arteries: In a compliance graph, which has a steeper slope?
Veins
Which part of the vasculature controls blood flow rate the most?
The arterioles changing their diameter
Flow Dependent Organs:
No tolerance for decreased blood flow: Brain and heart
Conditioning Organs
tolerant to lower levels of blood flow: Kidneys, Intestines, Skin
Active hyperemia
Increased metabolic activity-> causes decreased O2, increased metabolites->Arteriolar Dilation->Increased blood flow
Flow autoregulation
Decreased arterial pressure in the organ->decreased blood flow->decreased O2, increased metabolites, decreased vessel wall stretch->Arteriolar dilation->restoration of blood
Describe the myogenic response as it pertains to Ca2+
When pressure decreases in an organ, mechano gated Ca2+ will close more, decreasing Ca2+ available to provide contraction. This dilates the vessel, allowing more blood to come in.
List some metabolites that lead to vasodilation
Decreased O2 and pH, increased CO2, ECF K+, Adenosine
What is the effect of NO on smooth muscle?
Nitric Oxide relaxes the muscle, causing dilation.
Are alpha or beta2 receptor more common
alpha
Neural extrinsic control
NE is a vasoconstrictor that attaches to alpha receptors, NO is a vasodilator
Hormonal extrinsic control
Epinephrine is a vasoconstrictor when attaching to alpha receptors, and a vasodilator when attaching to beta 2 receptors.
Between the CA, CI, and VM, what is active at rest?
CA inactive, CI max, and VM partially activated.
What is conserved in a closed system? flow, velocity, or resistance?
Flow remains spatially conserved
Why is blood velocity through the capillaries slow?
The wider the diameter, to conserve flow rate, the slower the velocity must be. Since the capillaries TOGETHER have a very large diameter for flow in relation to the volume they take up, velocity is slow.
Capillary Diffusion: Plasma proteins
cannot get across capillary wall.
Capillary Diffusion: Lipid soluble substances
can pass through the endothelial cell walls
Capillary Diffusion: Small water soluble substances
can pass through small pores, except in the brain where glial cells cover this area with the brain blood barrier.
Capillary Diffusion: Exchangeable proteins
Moved across membrane by vesicular transport.
Filtration vs. Absorption
Filtration: Plasma to Interstitial Fluid
Absorption: Interstitial Fluid to Plasma
Hydrostatic Pressure
Direction of fluid flow has to due with pressure difference: “pushing force”
Osmotic Pressure
Gradient created for non diffusible molecules, water moves to minimize the gradient between the solutes. For example, in a salty solution, water moves out of a cell to decrease the solute to solvent ratio outside of the cell to be closer to that inside of the cell.
List of Starling Forces
Capillary hydrostatic pressure (Pc) and Interstitial hydrostatic pressure (Pif), Osmotic force due to plasma protein concentration (pi c) and Osmotic Pressure due to interstitial fluid protein concentration
Net Filtration Pressure
(Pc-Pif) + (pi if - pi c)
Autotransfusion
The body’s automatic homeotic response to blood loss–> capillary hydrostatic pressure falls, but this also puts the balance in favor of capillary osmotic pressure that pulls fluid in.
Application: Sick patient increasing fluid intake
increased fluid intake increases capillary hydrostatic pressure, and lowers the ratio of solutes in blood. These promote filtration, and increased lymph flow to filter out bad stuff.
Starvation
Decreased blood plasma proteins cause filtration, this can cause fluid to enter cells and enlarge the belly.
Edema
In case of stroke or heart failure, there in increase in venous pressure as heart is no longer pumping. Increased pressure capillaries, which causes more filtration.
5 helpful components for veins to work against gravity:
1) Sympathetic nerve firing causing constriction
2) One way valves
3) Skeletal muscle pumps
4) Breathing inspiration
5) High blood volume adds to pressure
Lymph System
Takes blood from vascular system, filters it and screens for disease, then returns it and helps with venous return
